America's Most Wanted's set resides in this tribute to the history of crime and punishment.

A surprising, but overlooked example of geology in the middle of the nation’s capital.

Washington's iconic carousel has a nice piece of Civil Rights history.

A little marble compass above George Washington's (empty) tomb in the Capitol marks where D.C.'s four quadrants intersect.

Where the U.S. government kept its actual treasure, before Fort Knox.

Obscure Freemasons still live in D.C.’s largest private residence.

A hoard of sky catalogs, astrophysical journals, even the works of Galileo and Copernicus.

Rumor has it the uncarved lump behind the three famous suffragists is reserved for the first woman president.

You could be standing at the site of one of D.C.'s most fatal tragedies and not even know it.

D.C.'s first central library was born out of a chance encounter with the philanthropist whose name it bears.

An obscure public service from the U.S. government that redeems burnt, moldy, and soiled old greenbacks.

An atomic bomb-proof strongbox protects the U.S. Constitution from terrorists and thieves.

When it opened during the final years of the embargo, all the drinks and cigars were free.

It was once the base for a series of domestic terror attacks.

The most decorated dog of World War I is preserved in the Smithsonian.

A three-story tower of books about Abraham Lincoln is one of the more unusual monuments to the president.

A nostalgic bibliographic gem.

The beloved statue at the National Academy of Sciences is oh so inviting to sit on.

The winding route passes through an enclosed alleyway, two tunnels, and leads to the White House basement.

A cavernous three-story, 43,800-square-foot basement that was forgotten about for 60 years.

During the Industrial Revolution this “Temple of Invention” was full of intricate miniature machines and gadgets.

A painfully obvious spy house sits right across the street from the Russian Embassy.

A monument in Washington D.C. marks the spot from which all other roads were supposed to stem.

There's a 12-foot-tall replica of the Washington Monument hidden under a manhole nearby.